FIG. 4 shows such a bolt tightening device which comprises planetary gear mechanisms 3, 4, 5 arranged inside a housing 10, an outer socket 7 coupled to one of two output shafts of the gear mechanism 5 in the terminal stage which are rotatable in directions opposite to each other, an inner socket 71 coupled to the other output shaft, and a motor 2 coupled to the input shaft of the first gear mechanism 3.
When the tightening device is to be used for a reaction-bearing bolt 8 passed through a plurality of members, such as a beam 9 and a channel member 91, a nut 85 is screwed on the bolt 8, and the device is operated with the outer socket 7 engaged with the nut 85 and the inner socket 71 with the tip 83. The nut can be tightened up with the tip 83 sustaining or bearing the reaction of tightening the nut.
Two types of reaction-bearing bolts 8 are available; one wherein the tip 83 merely bears a reaction, and the other wherein a groove 84 is formed between the threaded shank 81 and the tip 83, such that the tip 83 is twisted off from the grooved portion when subjected to a torque exceeding a predetermined value. For tightening upbolts of the former type, the tightening device has a torque limiter incorporated therein.
In either case, the tightening device has two sockets 7, 71 and a plurality of planetary gear mechanisms 3, 4, 5 which are arranged coaxilly, so that the housing 10 for holding these components has an increased length axially of the sockets 7, 71.
This entails the problem that when one side wall 91a of the channel member 91 which has a small groove width is to be fastened to the beam 9 with bolts, it is impossible to insert the tightening device into the groove of the channel member 91 for tightening the bolts.
Accordingly, the present applicants have made attempts to realize a tightening device having a great output and yet usable in narrow spaces by combining the device of FIG. 4 with a bolt tightening auxiliary tool 100 previously proposed by the applicants (see FIG. 3).
The auxiliary tool 100 of FIG. 3 comprises two coaxial input shafts 102, 101, two coaxial output shafts 103, 104 connected to an outer socket 7 and an inner socket 71 and displaced from the shafts 102, 101 in parallel thereto, and idle gears 61, 61 and 6, 6 interposed between the shafts 102, 103 and between the shafts 101,104, respectively. This arrangement reduces the thickness of the casing 105 axially of the sockets.
The auxiliary tool 100 is connected to two output shafts 201, 202 of a planetary gear mechanism 200, which has one input shaft 203.
A manual handle 14 is engaged with the shaft 203 of the mechanism and rotated, whereby bolts are tightened up.
In the case where three planetary gear mechanisms are connected to the auxiliary tool 100 of FIG. 3 coaxially therewith in place of the planetary gear mechanism 200, and two output shafts of the gear mechanism in the terminal stage are coupled to the inputs shafts 103, 104 of the outer socket 7 and the inner socket 71 by way of the idle gears 61, 61 and 6, 6 serving as two rotation transmitting systems, torques greatly reduced in speed and grealy increased in magnitude by the three gear mechanisms need to be transmitted by the idle gears 61, 6. The idle gears 61, 6 and the gears on the input shafts 103, 104 must therefore be made greater individually, consequently giving the casing 105 a larger thickness than is intended axially of the sockets.
An object of the present invention is to provide a bolt tightening device wherein a plurality of planetary gear mechanisms are arranged ingeniously to reduce the axial thickness of the device at its socket side and overcome the foregoing problem.